Iran has said five border guards kidnapped by Sunni Muslim militants are in good health, disputing a report that one of them had been killed.

The guards were seized while patrolling the lawless frontier with Pakistan in early February. Jaish al-Adl (Army of Justice), an Iranian Sunni Muslim rebel group in Sistan-Baluchistan province, later claimed responsibility.

"The kidnapped Iranian border guards are safe; there is no verified information to substantiate the terrorists' claim of murder of one of the kidnapped soldiers," official news agency IRNA quoted Iranian Deputy Foreign Minister Ebrahim Rahimpour as saying on Wednesday.

Jaish al-Adl said on its website last month that it had killed one border guard. Last week the semi-official Fars News Agency also reported that one of the border guards had been killed, quoting an "informed source".